Patly synthetic multigrade crankcase lubricant (law822)

ABSTRACT

A base oil for an SAE 0W-40 lubricant composition comprises a mineral basestock, a polyalpha olefin and synthetic ester lubricant. The SAE 0W-40 lubricant comprises the base oil and a mixture of polymethacylate and olefin copolymer or hydrogenated diene VI improvers.

FIELD OF THE INVENTION

[0001] The present invention relates to a multigrade crankcase lubricants that have good low and high temperature properties. More particularly the present invention relates to an SAE 0W-40 lubricant that contains both a conventional mineral basestock and a nonconventional or synthetic lubricant.

BACKGROUND OF THE INVENTION

[0002] Crankcase lubricating oils must provide minimal frictional wear in an engine over a wide range of operating temperatures. These engine temperatures can range from below freezing during cold weather starting to above 400° F. (200° C.) during severe usage. Lubricants which meet SAE viscosity specifications for both low and high temperatures are known as multigrade oils.

[0003] Blending basestocks of different viscosities is one way of formulating a multigrade oil. Merely blending basestocks of different viscosities, however, may not enable the formualtors to meet the low and high temperature viscosity requirements of some multigrade oils let alone other properties such as volatility and seal compatibility. The formulator's primary tool for meeting multigrade oil viscosity requirements is an additive referred to as a viscosity modifier.

[0004] An alternative means of reducing the basestock viscosity is to employ so-called non-conventional lubricants (or NCL). Examples of NCLs are synthetic basestocks such as polyalphaolefin oligomers (PAO) and diesters and specially processed mineral basestocks such as basestocks that have been hydrocracked or hydroisomerised to give greater paraffinic content and lower aromatic content. These NCLs, especially the diesters, are very expensive, may not respond well to conventional antioxidant systems, and may not be fully compatible with standard sealant materials.

[0005] Accordingly, it is an object of the present invention to provide an 0W-40 motor oil that has desirable low and high temperature properties.

[0006] It is another object to provide a motor oil that is a blend of conventional and non-conventional lubricants.

[0007] These and other objects will become apparent upon reading the description which follows.

SUMMARY OF THE INVENTION

[0008] A base oil for an SAE 0W-40 lubricant is provided comprising a mixture of mineral basestock, a polyalpha olefin and a synthetic ester lubricant. The SAE 0W-40 lubricant includes a viscosity improver, especially a mixture of VI improvers. Optionally, the lubricant includes antioxidant additives.

[0009] Engine lubricants containing the base oil of the present invention are capable of improving the fuel efficiency of an engine under conditions of use.

DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. The Base Oil

[0011] A. Mineral Basestock

[0012] The basestock used in the base oil may be selected from any of the natural mineral oils of API Groups I, II, III, IV or mixtures of these used in crankcase lubricating oils for spark-ignited and compression-ignited engines. Preferably, the mineral basestock is a Group II or III basestock having the properties shown in Table 1. TABLE 1 Pour Flash KV @ KV @ KV @ Point, Saturates, Sulfur, COC, 40° C. cSt 100° C. cSt 100° F. SUS VI ° C. wt % wt % ° C. 13.0-23.0 3.5-5.0 70-125 90-150 <−12 >75 <0.1 >170

[0013] B. The Polyalpha Olefin

[0014] The polyalpha olefin (PAO) used in the base oil may be selected from any of the olefin oligomer oils used in lubricants. In general the PAO will have a viscosity at 100° C. in the range of about 3.5 to about 4.5 cSt and preferably about 3.7 to about 4.2 cSt. Preferably the polyalpha olefin is one having the properties shown in Table 2. TABLE 2 Pour Flash KV @ KV @ KV @ Point, Saturates, Sulfur, COC, 40° C. cSt 100° C. cSt 100° F. SUS VI ° C. wt % wt % ° C. 16.0-18.0 3.7-4.2 85-100 115-135 <−60 >99.9 <0.01 >204

[0015] C. The Ester

[0016] Useful synthetic esters include the esters of monocarboxylic and polycarboxylic acids with monohydroxy alcohols and polyols. Typical examples include didodecyl adipate, diisodecyl adipate, pentaerythritol tetracaproate, and dilauryl sebacate. In general, the ester used will have a viscosity at 100° C. in the range of about 2 to about 4 cSt and preferably about 2.5 to about 3.5. Preferred properties for the ester are given in Table 3. TABLE 3 KV @ KV @ Pour Point, Flash COC, 40° C. cSt 100° C. cSt VI ° C. ° C. 8.5-14.0 2.5-3.5 110-160 <−60 >190

[0017] D. The Proportions

[0018] The base oil typically comprises to 5 to 80 vol % of the mineral basestock, 5 to 90 vol % of the polyalpha olefin and 1 to 30 vol % of the ester. Preferably, the base oil comprises 20 to 50 vol % of the basestock, 30 to 75 vol % polyalpha olefin and 3 to 20 vol % esters. In a particularly preferred embodiment the base oil comprises 25 to 45 vol % of the mineral base stock, 40 to 70 vol % of the polyalpha olefin and 3 to 20 vol % esters.

[0019] 2. VI Improvers

[0020] An SAE 0W-40 lubricant of the invention comprises the above base oil and VI improvers. VI improvers are components of lubricants which serve to decrease the viscosity changes in a lubricant with changes in temperature. Many different polymers are known to function as VI improvers. See for example, Smalheer, et al., Lubricant Additives, The Lezium-Hiles Company (1967), pages 8 and 9.

[0021] Of the many compounds known to be useful as VI improvers, alkyl methacrylate copolymers (PMA's) are recognized as having especially beneficial VI improver properties. Within this class, interpolymers of a short chain alkyl methacrylate, a long chain alkyl methacrylate and N,N-dialkylaminoalkyl methacrylate and/or methacrylamide (the alkyls of the dialkylaminoalkyl moiety having 1 to 6 carbon atoms) are particularly beneficial.

[0022] Typically VI improvers are formed in a hydrocarbon solvent and it is in this form that they are blended in the base oil.

[0023] Another group of VI improvers are olefin copolymers (OCP's) such as copolymers of ethylene and propylene.

[0024] These too typically are prepared in a solvent and are blended, in this form, in the base oil.

[0025] A third group of VI improver is hydrogenated diene copolymers which include styrene-hydrogenated diene block copolymers and hydrogenated star-branched polyisoprene. These polymers are made by an anionic polymerization process. They are typically available as a blend with a basestock and are added to the base oil as a blend.

[0026] The viscosity modifier used in the invention will be used in an amount to give the required viscosity characteristics. Since viscosity modifiers are often added to blends in the form of oil solutions the amount of additive employed will depend on the concentration of polymer in the oil solution comprising the additive. However, by way of illustration, typical oil solutions of polymer used as viscosity modifiers are used in amount of from 1 to 30% of the blended oil. The amount of viscosity modifier as active ingredient of the oil is generally from 0.01 to 6 wt %, and more preferably from 0.1 to 4 wt %.

[0027] In the present invention it is preferred to use both a PMA and a OCP or hydrogenated diene VI improver in amounts ranging from 3.0 to 7.0 vol % for the PMA VI improver and 4.0 to 9.0 vol % for the OCP or hydrogenated diene VI improver.

[0028] 3. DDI

[0029] The motor oil of the present invention has multifinctional additives of the type found in modern oil formulations. These additives are usually not added independently, but are precombined in DDI (detergent-dispersant-inhibitor) packages which can be obtained commercially from suppliers of lube oil additives. DDI packages with a variety of ingredients, proportions and characteristics are available.

[0030] 4. Antioxidants

[0031] Optionally, the motor oil may contain minor but effective amounts of antioxidants such as those used in contemporary motor oil formulations. A particularly preferred antioxidant comprises a mixture of alkylated diphenyl amine and hindered phenols.

EXAMPLES

[0032] The invention will now be described by way of illustration only with reference to the following examples. In the examples, unless otherwise noted, all treat rates of all additives are reported as volume percent active ingredient.

Examples 1, 2, and Comparative Examples A, B, C

[0033] Experimental SAE 0W-40 lubricants were made having the compositions given in Table 4. The Table also gives the acceptable property limits or targets and the actual measured properties for each formulation. TABLE 4 EXAMPLES COMPARATIVE EXAMPLES COMPONENTS 1 2 A B C Group II Basestock 26.76% 29.63% 29.38 vol % 26.34 vol % 28.76 vol % Durasyn 164¹ PAO 4 36.00 vol % 30.09 vol % 33.00 vol % 36.84 vol % 34.00 vol % Vistone A-10² Ester 10.00 vol % 16.56 vol % 15.00 vol % 11.00 vol % 10.00 vol % Oloa 9061E³ DI Package 13.44 vol % — — — 13.44 vol % Oloa 9015M³ DI Package — 12.52% 12.52 vol % 12.52 vol % — Paratone 8024⁴ OCP VI Improver  8.00 vol % — —  7.30 vol %  8.00 vol % Acryloid 953M⁵ PMA VI Improver  5.80 vol % — — —  5.80 vol % Acryloid 954⁵ PMA VI Improver — 6.00 vol    10.10 vol %  6.00 vol % — Shellvis 200C⁶ Star Copolymer VI Improver — 5.20 vol % — — — TARGETS KV @ 100° C. cSt 12.5-16.3 15.61 15.78 15.80 15.47 15.71 CCS @ −30° C., cP <2900 2810 2870 2950 2860 2870 Shear Stability, Viscosity >12.5 cSt 12.51 12.98 11.66 12.43 After ASTM D3945 TBS Viscosity, cP >3.7 4.03 4.24 4.10 4.11 MRV @ −40° C. cP <20,000 16,600 18,500 14,500 Pour Point, ° C. ≦−51 −51 −54 −54 −51 Noack Volatility <18% 17.8% 18.5% Comments: Not meeting Not meeting High Noack shear stability shear stability volatility

[0034] As shown in the above table, the right balance of the OCP and PMA VI improvers as well as the base oil components lead to formulations with excellent performance characteristics. Comparative formulations A, B, and C fail to meet the targets in one or more aspects. The formulation for Example 2, while meeting most of the performance targets, is less desirable because of the amount of synthetic ester. Indeed, oil formulations of this invention preferably contain less than 12 vol % of a synthetic ester lubricant.

Example 3

[0035] The fuel consumption of a Detroit Diesel series 60 engine was measured over a range of driving conditions using the OW-40 lubricant of Example 1. The results were compared with operating the same engine over the same driving conditions but using commercially available 15W40 oil. The percent increase in fuel efficiency is shown in Table V. TABLE V City Stop & Rolling Highway Go Level Highway Highway Mountains Fuel Efficiency 2.2% 1.06% 0.89% 0.63% Benefit 

What is claimed is:
 1. A base oil for an SAE 0W-40 lubricant comprising: about 5 to about 80 vol % of a mineral basestock; about 5 to 90 vol % of a polyalpha olefin lubricant and about 1 to 30 vol % of an ester lubricant.
 2. The base oil of claim 1 wherein the polyalpha olefin has a viscosity at 100° C. in the range of about 3.5 to 4.5 cSt and the ester has a viscosity at 100° C. in the range of about 2 to about 4 cSt.
 3. The base oil of claim 2 wherein the mineral basestock comprises 20 to 50 vol % of the base oil, the olefin lubricant from 30 to 75 vol % and the ester from 3 to 20 vol %.
 4. The base oil of claim 2 wherein the mineral basestock comprises 25 to 45 vol % of the base oil, the olefin lubricant from 40 to 70 vol %, and the ester from 3 to 20 vol %.
 5. An SAE 0W-40 lubricant comprising: a base oil consisting essentially of from about 5 to 80 vol % of a mineral basestock, from about 5 to 90 vol % of a polyalpha olefin lubricant and from about 1 to about 30 vol % of an ester lubricant; and a mixture of polymethacrylate and olefin copolymer or hydrogenated diene copolymer VI improvers.
 6. The lubricant of claim 5 wherein the polymethacrylate VI improver is present in an amount ranging from about 3 to about 7 vol % and the olefin copolymer or hydrogenated diene copolymer is present in an amount ranging from about 4 to about 9 vol %.
 7. The lubricant of claim 6 wherein the polyalpha olefin has a viscosity at 100° C. of about 3.5 to 4.5 cSt, and the ester of about 2 to 4 cSt.
 8. The lubricant of claim 7 wherein the base oil consists essentially of 20 to 50 vol % mineral basestock, 30 to 75 vol % polyalpha olefin and 3 to 20 vol % ester.
 9. The lubricant of claim 8 wherein the antioxidant is a mixture of alkylated diphenyl amine and hindered phenols.
 10. An engine lubricant capable of improving the fuel efficiency of the engine, the lubricant comprising: a base oil consisting essentially of from about 25 to 45 vol % of a mineral base stock, from about 40 to 70 vol % of a polyalpha olefin lubricant having a viscosity at 100° C. in the range of about 3.5 to about 4.5 cSt, from about 3 to 20 vol % of an ester having a viscosity at 100° C. in the range of about 2 to about 4 cSt; and a mixture of polymethacrylate and olefin copolymer or hydrogenated diene copolymer VI improvers wherein the polymethacrylate VI improver is present in an amount ranging from about 3 to about 7 vol % and the olefin copolymer or hydrogenated diene copolymer is present in an amount ranging from about 4 to about 9 vol % 